Runoff and Infiltration
Equipment Design
1. Rainfall Simulator
This is the Cornell Rainfall Simulator (Rainmaker)
and Infiltrometer, used for research by the Soil Health
Team at Cornell. Your goal is to design a simpler
version of this $1000 piece of equipment.
Here are the key characteristics of the rainfall
simulator:







A large enough volume to allow for about 10
min of rain
There must be a way to measure changes in
volume without moving the rainfall simulator
(i.e. by reading the change in volume from a
scale on the side of the rainfall simulator as the
water level is dropping; the Cornell version is
graduated on one side, A)
Very small holes at the bottom that allow for
rain-like drops (B)
The tube (C) must be able to reach almost to the
bottom, about 5-15 cm from the bottom. The level
of the bottom of the tube controls the rate at
which water is raining out of the rainmaker (i.e.
keeps it constant). It will rain faster when the tube
is higher off the bottom. The tube must stay in
place during measurement.
The rainmaker can be opened to add water (D)
When it is closed (D, a rubber stopper works,
depending on the design), the seal must be airtight. (Thus the airspace (E) is closed in, so this
slight vacuum, holds up the water above the
bottom of the tube. Atmospheric pressure now
pushes on the water only at the bottom of the
tube, not at the changing water level, so that
raindrops fall constantly and more slowly.)
It must fit over the Infiltrometer Ring or Sample
Container so that all rain falls inside the ring.
D
E
A
~10cm, C
B
2. Infiltrometer Ring for Outdoor Measurement
Total Rainfall
Soil Surface
Rubber Stopper
Outflow Tube
Runoff
Infiltration
3. Sample Container for Indoor Measurement


B
A

D

Infiltrometer base could be either a ring, or
could also be 4 sided wooden box
The outflow tube (or whatever outflow
channel can be attached to either a slot or
hole (A or B, B is the type of outflow used
on the Cornell set-up)
Soil is filled into the bucket/ring/box up to
the soil line (D), such that runoff can flow
out of the holes
Holes or a mesh in the bottom allow water to
pass through, but soil to remain in container
(C)
C
Option 1
A
For outdoor experiments:


Infiltrometer ring should be strong enough to
be able to be pushed or hammered into the
soil so that the outflow hole (A or B) is at the
level of the soil (D)
No mesh/holes (C) needed outdoors
B
Option 2
D
C
This material was developed through the Cornell Science Inquiry Partnership program (http://csip.cornell.edu), with
support from the National Science Foundation’s Graduate Teaching Fellows in K-12 Education (GK-12) program
(DGE # 0231913 and # 9979516) and Cornell University. Any opinions, findings, and conclusions or recommendations
expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.